SM200 Soil Moisture Sensor

Quick Start Guide Version 1.3

Delta-T Devices Ltd

© 2005 Delta-T Devices Ltd Page 2

SM200 overview

1 Cables

3 HH2

4 Data Loggers

2 Installation

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1 Cables and Accessories

1.1m 5m 10m 25m

5m bare end

Insertion rods are available for installing the SM200 in an augered hole.

2 Installation

Surface installation and spot measurements Clear away any stones. Pre-form holes in very hard

soils before insertion. Push the SM200 into the soil until the rods are fully

inserted. Ensure good soil contact. Best results are achieved by inserting the SM200 horizontally.

If you feel strong resistance when inserting the SM200, you have probably hit a stone. Stop, and re-insert at a new location.

Installing at depth Auger a 45mm diameter hole. ~10° to vertical is

recommended. Fit insertion rod to SM200 - remember to pass the

cable through the insertion rod and fit the connector first. Push the SM200 into the soil until rods are fully

inserted. Ensure good soil contact. Backfill around the insertion rod.

Alternatively Dig a trench, and install horizontally (see overview diagram).

HH2 cable

Extension cables

Logger cable Extension cables can be joined up to

a recommended maximum of 55m.

Align the connectors carefully before pushing parts together. Screw together firmly to ensure the connection is water-tight.

Power V+

Signal

Ground

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Device: v SM200

Soil Type: v Mineral

3 HH2 Meter

Connect the SM200 to the HH2 meter.

Press Esc to turn the meter on, and if necessary press again until the HH2 displays the start-up screen.

Set the meter to read from an SM200:

► Press Set and scroll down to the Device option.

► Press Set again and scroll down to select SM200.

► Press Set to confirm this choice.

Make sure the HH2 is correctly configured for your soil type:

► At the start-up screen, press Set and scroll down to the Soil Type option.

► Press Set again and scroll down to the appropriate soil type (use Mineral for sand, silt or clay soils or Organic for peaty soils)

► Press Set to confirm this choice.

Choose the units you want for displaying readings.

► At the start-up screen, press Set and scroll down to the Display option.

► Press Set again and scroll down to select units.

► Press Set to confirm this choice.

Press Read to take a reading.

Press Store to save or Esc to discard the reading.

Remove the SM200 from the soil and move to a new location...

If you have saved data, connect your HH2 to a PC and run HH2Read to retrieve the readings.

SM200 Store? 20.3%vol

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4 Data Loggers

GP1 2 SM200s can be connected to each GP1 - the SM200

should be connected as a single-ended, powered sensor.

These details illustrate connections for Channel1:

SM200 wiring Colour GP1 terminal Power V+ Red CH1 (PWR)

Signal White CH1 (+)

Ground Shield CH1 (GND)

and CH1 (-)

Configure the GP1 by choosing “SM200” from the sensor menu in PC DeltaLINK or Pocket DeltaLINK.

For configuration details see the GP1 Quick Start Guide.

DL6 Up to 6 SM200s can be connected to each DL6 with each

sensor connected as a single-ended, powered sensor.

These details illustrate connection to Channel1:

SM200 wiring Colour DL6 terminal Power V+ Red V+

Signal White IN+

Ground Shield IN-

and 0V

Configure the DL6 by choosing “SM200” from the sensor menu in DeltaLINK.

For configuration details refer to the DL6 User Manual.

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DL2e Up to 60 SM200s can be connected to each DL2e with

each sensor connected as a single-ended, powered sensor.

These details illustrate connection to Channel 58 using the LAC1 input card configured in 15-channel mode, and warm-up channel 63:

SM200 wiring Colour DL2e terminal Power V+ Red 63 NO

Signal White 58+

Ground Shield 58-

and 61-

Configure the DL2e by choosing one of the SM200 sensor codes from the LS2Win sensor library, according to your soil type.

For configuration details see the DL2e User Manual.

Other data loggers The SM200 should be connected as a single-ended, powered sensor.

Configure the logger input as a voltage sensor, approximately 0 to 1.0 volts corresponding to ~0 to 60% water content – see next section.

The SM200 has been optimised for a 1 second warm-up period (minimum period 200ms). It is recommended that the sensor is not powered continuously.

© 2005 Delta-T Devices Ltd Page 7

a0 a1 Mineral 1.6 8.4 Organic 1.3 7.7

Example

Take a reading with the SM200 V = 0.294 volts either Convert the reading to √ε using the polynomial or

linearisation table below. √ε = 3.62

Then convert √ε to soil moisture, θ, using the soil calibration values (a0, a1).

θ = 24.0%

or (for mineral soil) Convert directly for mineral or organic soils θ = 24.0%

5 Convert SM200 voltages to soil moisture readings

Note: The SM200 output is automatically converted to soil moisture when using an HH2 meter or Delta-T data loggers.

Conversion to √ε

Polynomial (use for SM200 readings from 0 to 1.1 Volts)

5432 536.13032.46881.60725.38103.160.1 VVVVV +−+−+=ε where V is the SM200 output in volts

Linearisation table (use for SM200 readings from 0 to 1.2 Volts)

V √ε V √ε V √ε V √ε V √ε 0.000 1.011 0.120 2.461 0.260 3.442 0.820 5.936 1.150 7.661

0.030 1.447 0.150 2.718 0.310 3.700 0.960 6.586 1.200 8.039

0.060 1.832 0.180 2.946 0.400 4.105 1.040 6.991 1.220 8.264

0.090 2.168 0.220 3.211 0.600 4.953 1.100 7.333 1.800 9.000

Conversion from √ε to Soil Moisture

Soil moisture ( ) 10 aa−= εθ

Use these generalised soil calibration values for mineral and organic soil types, or carry out a soil-specific calibration to derive your own values – see SM200 User Manual.

Multiply x100 to convert soil moisture from m3.m-3 to % volumetric.

Direct conversion for Mineral and Organic soils 5432

mineral 611.148.5248.761.4917.1071.0 VVVV +−+−+−=θ

5432organic 758.1978.5907.7029.5091.2039.0 VVVVV +−+−+−=θ

6 Specifications

* Accuracy figures apply to calibration soils and over 0 to 60°C. Percentages quoted as %vol are % volumetric water content. 7 Care and Safety

Notices All parts of the SM200 design and documentation are the exclusive property of Delta-T Devices and covered under international copyright law, © 2005. Patent(s) pending. The SM200 product is CE compliant, conforming to EN61326:1997.

Delta-T Devices Ltd 128 Low Road Burwell Cambridge CB5 0EJ England (UK)

Tel: +44 1638 742922 Fax: +44 1638 743155 E-mail: sales@delta-t.co.uk Web: www.delta-t.co.uk

The rods of the SM200 are sharp in order to ease insertion. Care must be taken and handling precautions followed.

Avoid touching the rods or exposing them to other sources of static damage. Keep the SM200 in its protective tube when not in use.

Take care when attaching cables to ensure that the connectors are clean, undamaged and properly aligned before pushing the parts together. Screw together firmly to ensure the connection is water-tight. If the connector is damaged, apply a light smearing of silicon grease to maintain sealing.

Do not pull the sensor out of the soil by its cable.

If you feel strong resistance when inserting the SM200 into soil, it is likely you have encountered a stone. Stop pushing and re-insert at a new location.

Range and Notes

Accuracy* ± 3 %vol 0 to 50 %vol

Salinity errors ± 3.5 %vol 0 to 40 %vol, over 50 to 500 mS.m-1 (0.5 to 5 dS.m-1)

Power requirement 5 to 14V 15mA typical

1 second warm-up recommended 200ms minimum

Output signal 0 to 1.0V Nominal 0 to 60 %vol

Environmental sealing IP68 Sensor buriable, sealed to IP68

Operating range -20 to +60°C Readings in frozen soil are not meaningful